The Environmental Protection Department (EPD) has recorded higher than normal pollution levels. At 2pm today (July 29), the Air Quality Health Index (AQHI) at some general and roadside stations had reached 8 or above, corresponding to the "Very High" health risk category.

Under the influence of the outer subsiding air of Typhoon Nesat, a continental airstream is affecting Hong Kong. The weather is mainly fine and very hot with moderate northerly winds. The intense sunshine enhances photochemical smog activities and the formation of ozone, resulting in high ozone concentrations in the Pearl River Delta region. The high level of ozone has promoted the formation of nitrogen dioxide particularly in parts of the urban areas and at the roadside. In addition, light winds hinder the effective dispersion of air pollutants. It is expected that the AQHIs of some general and roadside air monitoring stations may reach the "Serious" level later today.

According to the Hong Kong Observatory, Typhoon Nesat will track across Taiwan later today and move towards southeastern China tomorrow. It is expected that pollution levels will remain higher than normal until Nesat reaches the southeastern China coast.

With a health risk category in the "Very High" range or above, children, the elderly and persons with existing heart or respiratory illnesses are advised to reduce physical exertion and outdoor activities to a minimum or avoid such activities. The general public are advised to reduce, or reduce to a minimum, outdoor physical exertion, and to reduce time outdoors, especially in areas with heavy traffic. As health effects of air pollutants may vary for individuals, persons who are in doubt or experience discomfort should seek advice from health-care professionals. The public may visit the Centre for Health Protection's website (www.chp.gov.hk/en/content/9/460/3557.html) for more information on health effects of air pollution and relevant health advice.

When AQHI is at the "Very High" level, employers of outdoor workers performing heavy manual work are advised to assess the risk of outdoor work and take appropriate preventive measures to protect the health of their employees such as reducing outdoor physical exertion and the time of their stay outdoors, especially in areas with heavy traffic. At the "Serious" level, employers of all outdoor workers are advised to assess the risk of outdoor work and take appropriate preventive measures to protect the health of their employees.

Members of the public can check the current AQHI readings at the EPD's website (www.aqhi.gov.hk/en.html) or by calling the hotline 2827 8541.